shadow-style($width=4px,$color=rgba(0,0,0,.2),$inset=false)
  if $inset
    box-shadow: 0 $width * -1 $color inset
  else
    box-shadow: 0 $width $color

button-style($bg,$color=black)
  background-color: $bg
  color: $color
  &:hover
    background-color: lighten($bg, 3%)
  &:active
    background-color: darken($bg,3%)

distance(classname,prop,from=0,to=0,unit=10px)
  for i in (from..to)
    .{classname}{i * unit}
      {prop}: i * unit